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United States Patent | 5,241,444 |
Yeh | August 31, 1993 |
The disclosed fault indicator which senses current in a cable, resets in response to a minimum current and arms a trip arrangement in response to current rising a predetermined amount with respect to time. If the rising current also opens a circuit breaker within a predetermined time and cuts off current to the cable, the indicator trips. If no zero current occurs within the time period, the trip arrangement is disarmed for the next current rise.
Inventors: | Yeh; Thomas (South Weymouth, MA) |
Assignee: | Pacific Scientific Company (Weymouth, MA) |
Appl. No.: | 793223 |
Filed: | November 8, 1991 |
Current U.S. Class: | 361/59; 361/93.4; 361/95 |
Intern'l Class: | H02H 002/08; H02H 003/00 |
Field of Search: | 361/59,87,93,94,95,96,98,42 340/664 |
3673455 | Aug., 1972 | Dewey | 361/93. |
3715742 | Feb., 1973 | Schweitzer, Jr. | 361/69. |
3735248 | Feb., 1973 | Reese | 361/63. |
3959704 | May., 1976 | McCrea | 318/387. |
4223365 | Nov., 1980 | Moran | 361/96. |
4543570 | Dec., 1985 | Bressert et al. | 340/650. |
4733321 | Mar., 1988 | Lindeperg | 361/96. |
5029039 | Jul., 1991 | Yeh | 361/5. |
Foreign Patent Documents | |||
95590 | Feb., 1983 | EP. | |
244284 | Sep., 1987 | EP. | |
2048695 | Jul., 1972 | DE. |